A stroke occurs when blood flow to a part of the brain is interrupted, either by a blocked vessel (ischemic stroke) or a burst vessel (hemorrhagic stroke). This disruption deprives brain cells of oxygen and nutrients, causing them to die within minutes. Visible facial changes are common indicators that a stroke is occurring, demanding immediate attention, as prompt medical intervention can limit brain damage and improve recovery.
Visual Hallmarks of Facial Stroke
The most noticeable physical change following a stroke is sudden weakness or paralysis, known as facial droop, which typically affects only one side of the face. This unilateral weakness causes asymmetry, as the muscle tone on the affected side becomes slack, pulling the features downward.
The corner of the mouth often sags, leading to an uneven appearance when the person attempts to smile. This drooping can cause drooling because the weakened muscles cannot hold saliva effectively. The pronounced fold running from the side of the nose to the corner of the mouth, called the nasolabial fold, may appear flattened or smoothed out on the affected side.
In cases involving the cerebral cortex, the upper face is often spared, meaning the person can still wrinkle the forehead and raise the eyebrow on the affected side. However, the lower eyelid on the weakened side may pull down slightly. The inability to fully close the eye on the affected side is also possible, potentially leading to eye irritation or dryness.
The Neurological Basis of Facial Symptoms
Facial weakness during a stroke results from damage to the brain area controlling the facial muscles. This control is managed by motor pathways connecting the brain to the seventh cranial nerve (CN VII), which carries fibers that innervate the muscles used for facial expression.
In a stroke affecting the cerebral cortex, the resulting facial palsy is classified as an upper motor neuron lesion. A characteristic of this damage is that the upper face muscles (forehead and eyebrow) receive nerve input from both sides of the brain, so they are often spared. Conversely, the lower face muscles receive input only from the opposite side of the brain and become weak or paralyzed.
Since the brain controls the opposite side of the body, a stroke in the left hemisphere typically causes facial weakness on the right side of the face. The extent and pattern of the weakness depend on the location and size of the brain lesion. Damage to the brainstem, for instance, can affect the facial nucleus itself, leading to complete weakness across the entire side of the face, including the forehead.
Recognizing Symptoms: The FAST Protocol
The most widely recognized and effective method for identifying stroke symptoms quickly is the FAST acronym, which stands for Face, Arms, Speech, and Time. Focusing on the “F” for Face, an immediate test is to ask the person to smile or show their teeth.
If a stroke is occurring, the smile will appear lopsided or uneven because one side of the mouth will not move upward. This confirms the facial asymmetry that is a hallmark of the event. The “A” and “S” components check for sudden arm weakness and slurred or confused speech, which are other common stroke indicators.
The final letter, “T,” for Time, emphasizes the need for immediate emergency medical attention if any symptoms are observed. Time is a factor because the effectiveness of stroke treatments, such as clot-busting drugs, decreases significantly as the time from symptom onset increases. Calling emergency services right away is necessary, even if symptoms disappear, as a transient ischemic attack (TIA) presents similar symptoms and is a serious warning sign.
Duration and Potential for Long-Term Facial Changes
The duration and extent of facial changes after a stroke depend on factors like the size of the stroke and the speed of treatment. Individuals who experience a transient ischemic attack may find that their facial weakness resolves within a few minutes or hours. For others, the symptoms may persist, requiring a focused recovery process.
Facial symptoms often improve over time, with many patients regaining normal or near-normal facial function within months. However, long-term residual weakness or noticeable asymmetry can remain. Physical rehabilitation, involving targeted exercises, helps patients regain control over the affected facial muscles and improve symmetry.